This invention relates to the mechanical harvesting of trellis-supported grapevines.
A typical vineyard consists of a series of rows of stakes which support an arrangement of horizontal and parallel trellis wires running along the rows to form a trellis system for supporting the individual grape vine growth and the attendant fruit thereon. A generally vertical vine trunk is typically located at each stake with the cordons or canes of the vine being trained longitudinally on and along the trellis wires. The layout of the modern vineyard is relatively standardized with about 500 vines per acre.
All commercially succesful harvesting machines to date have been based on some means of agitating or shaking the vines and fruits to cause detachment of the fruit.
For example, striker rod machines use a series of striker rods which swing back and forth, into and out of the foliage, to dislodge the fruit largely by direct contact. Typically, four banks of 3-foot long, 3/4-inch diameter fiberglass rods are positioned in vertical planes with the rods being oscillated horizontally baout their forward ends so that the free ends of the rods whip back and forth rapidly to strike the grapes from the vines. The striker rod type of harvester is exemplified by U.S. Pat. No. 3,688,428 to D. Horn, and U.S. Pat. No. 4,016,711 to G. Claxton.
In recent years, machines have been developed for shaking the vine trunks and trellis system to remove the fruit. In particular, this system uses opposed shaker rails which engage the vine trunks and/or trellis parts therebetween as the machine travels down the row. The shaker rails are oscillated back and forth rapidly to shake the vines so that the inertia of the fruit will cause the fruit to be dislodged from the shaking vine. Examples of shaker rail harvesters are shown in U.S. Pat. Nos. 4,179,871 and 4,198,801 to G. Claxton.
Additionally, harvesting machines of the shaker-striker type are presently in commercial use, combining the use of pivotal striker rods and oscillating shaker rails to cause fruit removal. An example of a shaker-striker machine is shown in U.S. Pat. No. 4,250,700 to D. Horn and G. Claxton.
With regard to the shaker rail type harvester, there have been various ways in which the shaker rails have been mounted for back and forth horizontal movement transverse to the row being harvested. Typically in commercial harvesters, a picking head frame is mounted on the harvesting machine frame, with the picking head frame being free to swing back and forth so that the picking head can center itself on the row of vines being harvested.
In one relatively early arrangement, the shaker rails were mounted on the picking head frame by telescoping slides, as shown in U.S. Pat. No. 4,172,352 to Mr. McCarthy et al., so that the rails are translated back and forth relative to the picking head frame.
Another type shaker-rail suspension is shown in the above mentioned U.S. Pat. No. 4,198,801, to G. Claxton, wherein the rails are suspended from the picking head frame by a link arrangement so that the shaker rails swing back and forth relative to the vine. A drive unit acting between the shaker rails and the picking head frame moves the shaker rails back and forth.
Yet another type of shaker rail suspension is that shown in U.S. Pat. No. 4,286,426 to Orlando and Fitzmaurice and U.S. Pat. No. 4,336,682 to Orlando, wherein the shaker rails are essentially integral with the picking head frame, and the entire picking head frame is oscillated so that the shaker rails move back and forth relative to the main frame of the machine.
The present invention is particularly directed to this latter general type of machine.
In the particular form of this type of machine which is shown in U.S. Pat. Nos. 4,286,426 and 4,336,682, the picking head frame is driven by two sets of eccentric weights, symmetrically arranged one on each side of the picking head frame, which are rotated about horizontal axes parallel to the longitudinal axis of the main harvester frame.
One particular drawback of this arrangement is that considerable reaction forces are transmitted from the oscillating picking head frame back into the main frame of the machine. This reaction force results from the fact that the picking head frame is mounted on the main frame so that the center of rotation of the picking head is fixed relative to the main frame of the machine and above the center of gravity of the picking head.
As the two sets of weights rotate, vertical forces, with a moment arm equal to the distance from the center of the weights to the center of rotation, i.e. the axis of pivotal movement, will cause the picking head frame unit to oscillate about its pivotal center of rotation. At the same time, since the center of gravity of the system is not at the center of rotation, the center of gravity will move horizontally back and forth as the picking head oscillates, and with a reactive force equal to the dynamic mass of the picking head times the acceleration of the movement of the center of gravity. There is no way in this system wherein the forces can be balanced, and thus there will be a reactive moment acting on the pivotal connection (and back into the main frame of the machine) equal to the dynamic mass of the picking head times the acceleration of the center gravity times the distance between the center of gravity and the axis of rotation.
The reactive force can be decreased by decreasing the distance between the center of gravity and the axis of rotation. However, the center of gravity is designed to be below the axis of rotation so that the picking head will hang downwardly and center itself in the machine. A decrease in the distance will lessen the described centering effect. Thus, a reduction in the distance between the center of gravity and the axis of rotation will desirably reduce the reactive forces transmitted back into the frame but will undesirably reduce the centering ability, and vice versa. As a consequence, self centering cannot be achieved without an attendant reactive force that will be transmitted back into the main frame of the harvester.
Another drawback of the arrangement shown in U.S. Pat. Nos. 4,286,426 and 4,336,682 is that as the shaker rails are driven back and forth horizontally, they will be driven in one direction with markedly less force than in the other, so that the "snapping" action (needed for fruit removal) at the end of movement in that direction is correspondingly lessened. The difference in force is due to the fact that the two sets of weights, one on each side of the centerline, are both belt-driven in the same direction of rotation from drive pulleys coaxial with the center of rotation of the picking head frame. As a consequence, there is a force equal to the sum of the tensions in the two drive belts times the radius of the drive pulley which adds to the force of the eccentric weights in one direction of picking head rotation and subtracts from the eccentric weight force in the opposite direction of picking head rotation.
Yet another disadvantage of the arrangement shown in U.S. Pat. Nos. 4,286,426 and 4,336,682 is that the overall height of the picking head unit is undesirably great, requiring a harvesting machine with a high main frame, thus increasing the potential for instability in a sloping vineyard. The main frame brackets on which the picking head is mounted, and the portion of the picking head vertically above the shaker rails must be high enough off the ground so that the machine can clear the tops of the grape stakes and the heavy anchor posts at the ends of the row. As is seen from these patents, the supports for the picking head and the picking head itself extend physically below the fixed axis of pivotal movement. Also, the center of gravity of the picking head is slightly above the lowermost parts of the picking head which are vertically above the shaker rails. In order to have such a high center of gravity, and to accommodate the use of weights which rotate about horizontal axes, the picking head must extend vertically a significant distance above its axis of pivotal movement. Then, in order to suspend the picking head from the main frame of the harvester and to allow its oscillating movement relative to the main frame, the main frame must have a very significant height above the ground.
As is apparent from the foregoing, there is a need for a mechanical grape harvester of the shaker rail type with an oscillating frame wherein there is a minimum of reactive force transmitted back into the main frame, wherein the shaker rail forces are the same in either horizontally transverse direction relative to the row being harvested, and wherein the overall height of the picking head can be minimized.